Be careful about digging. You could 'undermine' the foundation! Even though the house is 100 years old, one of the reasons it's STILL standing is because the footing/foundation is sufficiently deep enough, below grade. If you take out too much dirt, your walls could start moving inwards.
If you're serious about this, I'd consider hiring a Structural Engineer to evaluate your options. The few 100 $$$s it will cost is $$$ WELL spent (out of your pocket.)